1. Field of the Invention
The present invention relates to a process control technique in a semiconductor manufacturing system, and more specifically, to a process control technique that includes an apparatus for processing a prescribed number of wafers at once.
2. Description of the Background Art
A manufacturing process of semiconductor devices includes a diffusion step which is one of the steps in which a prescribed number of wafers are processed at once. In the diffusion step, a diffusion layer including impurities is formed on a wafer. In this step, a prescribed number of wafers that have the same processing condition (such as type of a diffusion film to be formed) are processed at the same time. When the processing in the diffusion step is completed, the wafers are provided to the next step (for instance, a photolithography step for transferring a pattern thereon, a chemical treatment step and the like).
In the diffusion step, in addition to product wafers, monitor wafers and dummy wafers are processed at the same time. Monitor wafers are wafers for inspection of diffusion processing. Measurement of a film thickness and the like of monitor wafers after diffusion processing are performed by a prescribed inspecting apparatus. Dummy wafers are used when the number of product wafers in the diffusion step is smaller than the prescribed number. This is to allow uniform processing in a diffusion furnace. These monitor wafers and dummy wafers are referred to as non-product wafers. These non-product wafers have their diffusion layers, which are formed in the diffusion step, processed by chemicals and the like and thus are restored to the condition before the diffusion processing. The recycled non-product wafers are once again processed in the diffusion step. This recycling processing is performed in a chemical treatment step that also processes the product wafers.
Japanese Patent Laying-Open No. 10-321486 discloses a control apparatus for controlling processing including reproduction or recycling and disposal of such non-product wafers. The control apparatus disclosed in this publication is an apparatus for controlling diffusion processing, reproduction processing, disposal processing and the like of the non-product wafers in a semiconductor manufacturing system. The control apparatus includes an ID (identification) marking circuit for marking on a non-product wafer a wafer ID which includes identifying information and type of the non-product wafer; a storage circuit for storing, for each wafer ID, discrete information including information on number of times the non-product wafer has been recycled and the period of use of the non-product wafer; a master information storage circuit for storing, for each type of the non-product wafer, master information including information on the limit of number of times of recycle, the service life limit, and recycling procedure; an ID reading circuit for reading the wafer ID; a determining circuit for determining on one of reproduction processing and disposal processing based on master information and discrete information of the wafer ID read by the ID reading circuit; and a control circuit for issuing a recycling procedure instruction corresponding to the wafer ID when the result of determination is reproduction processing, and for instructing to reject the non-product wafer corresponding to the wafer ID and rejecting the wafer ID included in the discrete information when the result of determination is disposal processing.
According to this control apparatus, marking of a wafer ID, reading of the wafer ID, and the determination based on the master information and the discrete information of the read wafer ID are automatically performed. As a result, accidents in reproduction processing can be prevented due to elimination of mistakes made by an operator, and reduction in the quantity of non-product wafers used can be achieved by controlling the non-product wafers in a unified manner.
In some cases, mere issuing of the recycling procedure instruction may not bring about the actual recycling processing of the non-product wafers. When the recycling processing is not performed while the quantity of non-product wafers used is being reduced, a shortage of dummy wafers or monitor wafers would take place. In this case, even when the product wafers are made ready for the processing, the non-product wafers cannot be made ready so that processing such as in the diffusion step cannot be performed. In particular, such a problem occurs when the recycling processing is performed in the chemical treatment step for processing the product wafers, because, in the chemical treatment step, the processing of the product wafers is put before the recycling processing of the non-product wafers even when there is a recycling procedure instruction.
An object of the present invention is to provide a process control apparatus and a method that allow preparation of non-product wafers with high efficiency in a semiconductor manufacturing process.
Another object of the present invention is to provide a process control apparatus and a method that allow preparation of non-product wafers with certainty in a semiconductor manufacturing process.
A further object of the present invention is to provide a process control apparatus and a method that can improve an availability ratio of a processing step for processing product wafers in a semiconductor manufacturing process.
A still further object of the present invention is to provide a process control apparatus and a method that allow control of non-product wafers with high efficiency in a semiconductor manufacturing process.
A process control apparatus according to the present invention controls a semiconductor manufacturing system including a processing apparatus for batch-processing a prescribed number of wafers at once and a recycling apparatus for recycling wafers processed by the processing apparatus. The processing apparatus processes the wafers based on a predetermined processing condition. The prescribed number of wafers include product wafers and non-product wafers. The recycling apparatus recycles the non-product wafers. The recycled wafers are repeatedly processed by the processing apparatus. The process control apparatus includes a communication circuit for communicating with the processing apparatus and the recycling apparatus, a storage circuit for storing recycling processing procedure corresponding to the processing condition, a detection circuit connected to the communication circuit for detecting non-product wafers included in the processed wafers when the batch-processing by the processing apparatus is completed, and an instructing circuit connected to the communication circuit, the storage circuit, and the detection circuit for instructing the recycling apparatus to perform recycling processing on the detected non-product wafers based on the recycling processing procedure corresponding to the processing condition that was used when the non-product wafers were processed by the processing apparatus.
The non-product wafers are recycled in the recycling apparatus by an instruction from the process control apparatus to the recycling apparatus. Even in the case where the recycling processing procedures differ due to the processing conditions in the processing apparatus, the preparation of the non-product wafers prior to the next processing in the processing apparatus can be ensured. As a result, a process control apparatus in a semiconductor manufacturing system can be provided which can improve the availability ratio of a processing step for processing the product wafers by preparing the non-product wafers with high efficiency and certainty.
More preferably, the process control apparatus includes a counting circuit for counting a number of times the non-product wafers are processed by the processing apparatus, and a control circuit connected to the detection circuit and the counting circuit for controlling the instructing circuit to interrupt the instruction when a number of times the detected non-product wafers are processed exceeds a predetermined number of times.
The number of times the non-product wafers are processed are counted, and when it exceeds a predetermined number of times, the recycling processing can be interrupted so as not to allow recycled use. Thus, excessive recycling can be prevented.
More preferably, the recycling apparatus batch-processes a prescribed number of wafers at once. The semiconductor manufacturing system further includes a stocking unit disposed between the processing apparatus and the recycling apparatus. The stocking unit stocks a prescribed number wafers required for processing in the recycling apparatus. The communication circuit includes a circuit for communicating with the stocking unit as well as with the processing apparatus and the recycling apparatus. The process control apparatus further includes a stocking unit control circuit connected to the communication circuit for controlling the stocking unit to discharge the non-product wafers to the recycling apparatus from the stocking unit when a prescribed number of the non-product wafers required for processing in the recycling apparatus are stocked.
The prescribed number of non-product wafers required for processing in the recycling apparatus are stocked before being supplied into the recycling apparatus. The prescribed number of wafers are supplied each time to the recycling apparatus so that the availability ratio of the recycling apparatus can be improved, and the non-product wafers can be prepared prior to the processing that succeeds the diffusion processing step.
More preferably, the process control apparatus further includes a reception circuit connected to the communication circuit for receiving an accept request from the recycling apparatus. The stocking unit control circuit includes a circuit for controlling the stocking unit to discharge the non-product wafers to the recycling apparatus from the stocking unit when the prescribed number of non-product wafer required for processing in the recycling apparatus are stocked and when the reception circuit receives the accept request from the recycling apparatus.
Even if the recycling apparatus also performs the processing for the product wafers, the non-product wafers can be supplied into the recycling apparatus based on the accept request from the recycling apparatus. Thus, the availability ratio of the recycling apparatus can be improved, and the non-product wafers can be prepared prior to the processing that succeeds the diffusion processing step.
A method of process control according to another aspect of the present invention controls a semiconductor manufacturing system that includes a processing apparatus for batch-processing a prescribed number of wafers at once and a recycling apparatus for recycling wafers processed by the processing apparatus. The processing apparatus processes the wafers based on a predetermined processing condition. The prescribed number of wafers include product wafers and non-product wafers. The recycling apparatus recycles the non-product wafers. The recycled wafers are repeatedly processed by the processing apparatus. The method of process control includes the steps of preparing recycling processing procedure corresponding to the processing condition, detecting non-product wafers included in the processed wafers when the batch-processing by the processing apparatus is completed, and instructing the recycling apparatus to perform recycling processing on the detected non-product wafers based on the recycling processing procedure corresponding to the processing condition that was used when the non-product wafers were processed by the processing apparatus.
When the batch-processing in the processing apparatus is completed, non-product wafers are detected. The recycling apparatus is instructed to perform recycling processing on the detected non-product wafers based on the recycling processing procedure corresponding to the processing condition in the processing apparatus. Thus, the non-product wafers are recycled in the recycling apparatus by an instruction to the recycling apparatus according to the process control method. Even in the case where the recycling processing procedures differ due to the processing conditions in the processing apparatus, the preparation of the non-product wafers prior to the next processing in the processing apparatus can be ensured. As a result, a method of process control in a semiconductor manufacturing system can be provided which can improve the availability ratio of a processing step for processing the product wafers by preparing the non-product wafers with high efficiency and certainty.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.